Suction filter, turbo compressor and method for compact assembling of the same

ABSTRACT

A casing provided centrally with a sealed structure chamber. Small-sized separate four filter elements are arranged each on opposite sides of the chamber such that inflow air from a suction section into the casing is introduced via the filter elements into the chamber. Each filter element is detachably fitted over a filter-element mount having openings at its outer periphery. Upon filter-element replacement, the filter elements are replaced individually by opening a window. An integral cast casing having compressing sections and compressed air passages integrally fabricated therewith by casting is formed with receptacles for first and second intercoolers and an aftercooler. The intercoolers and aftercooler are received in the receptacles. Outlets of the intercoolers are connected with suction sides of second- and third-stage compressors through second- and third-stage suction pipes, respectively. A blowoff silencer is arranged between the integral cast casing and an oil tank.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a division of U.S. patent application Ser.No. 10/544,786, filed on Aug. 8, 2005, which is incorporated in itsentirety herein by reference. U.S. application Ser. No. 10/544,786 is anational stage application of PCT/JP04/03771 filed Mar. 19, 2004.

This application also claims priority under 35 USC §119 to JPapplication nos. 2003-085407, filed Mar. 26, 2003 and JP 2003-100336,filed Apr. 3, 2003.

TECHNICAL FIELD

The present invention relates to a suction filter on a suction side of asuction line for a compressor. The invention further relates to aturbocompressor, in particular, a turbocompressor in which compressingsections as compressor bodies are assembled together with air coolersand a silencer into a compact assembly and a method for compactassembling of the turbocompressor.

BACKGROUND ART

First, a background art on a suction filter will be described.

Among turbocompressors, a two-stage turbocompressor has been proposed asexemplarily and schematically shown in FIG. 1. More specifically, afirst-stage compressor 1 is connected at its suction port 2 to a suctionline 4 with a suction valve 3 midway thereof. The suction line 4 has, atits one end or on its suction side, a suction filter 5 with a filterelement 6 for removal of foreign matter such as dust. The first-stagecompressor 1 is connected at its discharge port 7 to a suction port 9 ofa second-stage compressor 8 via a line 10 with an intercooler 11 whichcools compressed air to be introduced into the second-stage compressor 8for reduction of a volume thereof. The second-stage compressor 8 isconnected at its discharge port 12 to a discharge line 13 with anaftercooler 14. The line 13 is branched downstream of the aftercooler 14into a compressed air supply line 15 and a blowoff line 16. Thedischarge line 13 downstream of the branched point is provided with apressure switch 17 which controls opening and closing of the suctionvalve 3 and of a blowoff valve 18 in the blowoff line 16 (See JP8-121398A).

As disclosed in said JP 8-121398A, the suction filter 5 employed in theconventional turbocompressor comprises, as shown in FIG. 2, a casing 19with a suction section 20, a discharge section 21 centrally of thecasing 19 and communicated with the suction line 4, a large-diameterfilter-element mount 22 having peripheral openings communicated with thedischarge section 21 and a large-sized cylindrical filter element 6fitted over the mount 22; air sucked through the suction section 20opened on a portion of the casing 19 is introduced via the filterelement 6 into the discharge section 21 and during such passage of theair the foreign matter such as the dust is removed from the air.

As illustrated, most of such conventional suction filters 5 have thesingle filter element 6 for the single discharge section 21. Therefore,when replacement of the filter element 6 becomes required during anoperation of the compressor due to, for example, clogging of theelement, no problem will occur provided that the operation of thecompressor can be stopped; however, there may be some cases where thesingle filter element 6 has to be replaced without stoppage of theoperation of the compressor; then, removal of the single filter element6 for replacement with another one will inevitably bring about nosealing or covering of the opening on the filter-element mount 22 due tothe removal of the filter element 6 since suction of air must becontinued. As a result, a lot of air is sucked through the uncoveredopening on the filter-element mount 22 and there may be a fear that alot of foreign matter such as dust to be removed by the filter element 6is sucked without filtering during the replacement work of the filterelement. Furthermore, replacement of the filter element requires muchtime and manpower since the filter element 6 is so large as to behandled by a crane and is hard to be treated.

Accordingly, an object of the invention is to reduce or remove the riskof a lot of foreign matter being sucked even at a replacement work ofthe filter element during the operation of the compressor and to conductthe replacement work readily and in a small amount of time.

Next, a background art relating to a turbocompressor and a method forcompact assembling of the same will be described.

As a turbocompressor used for preparation of compressed air to besupplied to a demand such as a plant, there have been known two- andthree-stage turbocompressors depending upon compressed air pressurerequirement.

The two-stage turbocompressor is constructed such that it has first- andsecond-stage compressors with a rotary shaft rotated via a mechanism forspeeding up a drive force from a motor to rotate impellers incompressing sections. Air sucked through a suction filter is compressedby the first-stage compressor and is discharged via a discharge port ofthe first-stage compressor into an intercooler which is an air cooler.Then, the compressed air from an outlet of the intercooler is introducedinto the second-stage compressor so as to be compressed. The air thuscompressed in the second-stage compressor is introduced into anaftercooler which is an air cooler, and is supplied via an outlet of theaftercooler to the demand. During the supply to the demand beingstopped, the air is blown off from the aftercooler via a blowoff pipe, ablowoff silencer being arranged downstream in the blowoff pipe.

The three-stage turbocompressor is constructed such that provided aretwo or first and second intercoolers and a third-stage compressor. Airsucked through a suction filter is compressed by a first-stagecompressor and is discharged via a discharge port of the first-stagecompressor into the first intercooler. The compressed air discharged viaan outlet of said first intercooler is introduced into the second-stagecompressor so as to be compressed. The air thus compressed by thesecond-stage compressor is introduced into the second intercooler and isthereafter introduced from said second intercooler into the third-stagecompressor so as to be further compressed. The air thus compressed bythe third-stage compressor is introduced into the aftercooler and issupplied via an outlet of the aftercooler to the demand. During thesupply of the compressed air to the demand being stopped, the compressedair is blown off from the aftercooler via the blowoff pipe, noisedeadening being effected by a blowoff silencer at a downstream end ofthe blowoff pipe so as to prevent the noise from being generated duringblowoff.

In such two- or three-stage turbocompressor, conventionally the blowoffsilencer at the downstream end of the blowoff pipe is not mounted on thecompressor but is arranged separately to be connected to the blowoffpipe; in this case, the silencer itself is made longer to increase anamount of sound absorbed. On the compressor, a simple muffler ismounted.

The blowoff silencer not mounted on the compressor but arrangedseparately in the two-stage turbocompressor has been proposed (See, forexample, JP 2001-289168A).

The two-stage turbocompressor has been known in which integrallyfabricated by casting are compressing sections of the first- andsecond-stage compressors, a receptacle for a power transmissionmechanism which transmits a drive force for compressing operations ofthe compressing sections, a cooler casing for two air coolers,compressed air passages connecting the first- and second-stagecompressors to the air coolers, respectively, the two air coolers beinghoused in said cooler casing in a partitioned manner (See, for example,JP 8-93685A and JP 10-252681A).

In the three-stage compressor, as schematically shown in FIG. 3, first-,second- and third-stage compressors 31, 32 and 33 are arranged; adischarge port of the first-stage compressor 31 and a first intercooler34 are interconnected by a compressed air passage 37 so as to beintegrally structured; an outlet of the first intercooler 34 and asuction port of the second-stage compressor 32 are interconnected by acompressed air passage 38 so as to be integrally structured; thesecond-stage compressor 32 and a second intercooler 35 areinterconnected by a compressed air passage 39 so as to be integrallystructured; and an outlet of the second intercooler 35 and an suctionport of the third-stage compressor 33 are interconnected by a compressedair passage 40 so as to be integrally structured. The third-stagecompressor 33 is connected via a compressed air passage 41 to anaftercooler 36. In such structure, integrally fabricated by casting intoan integral cast casing in the same manner as in the two-stagecompressor mentioned above are compressing sections of the respectivestage compressors 31, 32 and 33, a receptacle for a power transmissionmechanism which transmits a drive force for compressing operations ofthe respective compressing sections, a receptacle for two intercoolers34 and 35 and compressed air passages 37, 38, 39 and 40 sequentiallyinterconnecting the first-stage compressor 31, the first intercooler 34,the second-stage compressor 32 and the second intercooler 35. Only thetwo intercoolers 34 and 35 are incorporated in the integral cast casing;separately arranged is the aftercooler 36 to which the discharge port ofthe third stage compressor 33 is connected via an extension of thecompressed air passage 41.

The blowoff silencer not mounted on the compressor but arrangedseparately as shown in JP 2001-289168A has problems that constructingthe blowoff pipe is much troublesome and that space for installing thesilencer must be ensured. On the other hand, in a case where the blowoffsilencer is mounted on the compressor, no problem will occur ifsufficient space for installation of the silencer is secured; however,if the place cannot be secured for the reason of, for example, spacesaving of the compressor, the silencer itself has to be made compact andsimple, resulting in insufficient noise deadening.

In the two-stage turbocompressor in the form of integral cast casting asshown in JP 8-93685A and JP 10-252681A, the compressing sections of thecompressors and the compressed air passages are integrally fabricated,so that the two-stage turbocompressor is applicable only for two-stagecompression; similarly, a three-stage turbocompressor is applicable onlyfor three-stage compression. Accordingly, the three-stage compressorcannot be used for, for example, one or two-stage compression andtherefore cannot cope with special use.

Furthermore, though the two-stage turbocompressor may be in the form ofintegral cast casing with two air coolers being incorporate therein asshown in JP 8-93685A and JP 10-252681A, there has been no three-stageturbocompressor with three air coolers being incorporated in an integralcast casing; in fact, generally only two intercoolers are incorporatedin the integral cast casing and the aftercooler is arranged separatelyor placed centrally.

Accordingly, there are problems that the number of the parts isincreased and that the structure is made larger due to increase ofinstallation area caused by such separate arrangement; the air pipe forconnecting the third-stage compressor with the aftercooler must beextended, which leads to increase in pressure loss and thusdeterioration in performance. JP 8-93685A and JP 10-252681A do not showthree coolers incorporated in a casing in a three-stage turbocompressorat all.

Thus, an object of the invention is to provide a turbocompressor whichcan achieve space saving with respect to installation of a blowoffsilencer so as to enhance noise deadening effect and which may be athree-stage turbocompressor compact in size and easily cope with one ortwo-stage compression.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned problems, a suction filteraccording to the invention comprises separate filter elements arrangedin an air flow path from a suction section to a discharge section, airsucked through each of said filter elements being introduced into saiddischarge section; filter elements may be laterally separately arrangedin a casing with suction and discharge sections, air sucked through saidlaterally separated filter elements being introduced into said dischargesection. As a result, when a filter element replacement work is to beconducted, one filter element can be replaced while the remaining filterelements can continue sucking the air. During replacement of the filterelement, an amount of air sucked through the filter-element mount fromwhich the filter element has been detached for replacement may be alittle, so that a probability of the foreign matter being sucked can bereduced. In this respect, even when the opening on the filter-elementmount from which the filter element has been detached is closed, thewhole resistance is still smaller and hardly affects on the operation ofthe compressor; such closing of the opening ensures no foreign matter tobe sucked through the mount from which the filter element has beendetached.

The casing may be provided centrally therein with a chamber which is asealed structure, separate filter elements being arranged on oppositesides of the chamber, an interior of the sealed structured chamber beingcommunicated with an exterior of the chamber through the respectivefilter elements and communicated with the discharge section. Thisenables a number of filter elements to be arranged on opposite sides ofthe chamber and thus enables the filter elements to be smaller in sizeso that opening areas on the filter-element mounts may be smaller, whichleads to further reduction in probability of foreign matter being suckedduring the filter element replacement work.

The casing outside of the filter elements may have sides each formedwith a window corresponding the whole size of the filter elementsarranged on the side, said window being adapted to be sealed by a lidwhich can be opened and closed. Thus, replacement of each filter elementcan be readily conducted through the corresponding window.

In order to overcome the above-mentioned problems, a turbocompressor anda method for compact assembling of the same according to the inventioncomprises an integral cast casing with first-, second- and third-stagecompressors and with all of air coolers corresponding to saidcompressors being incorporated therein, said respective stagecompressors being connected to the corresponding air coolers throughcompressed air passages, respectively, the incorporated air coolers inthe integral cast casing being first and second intercoolers and anaftercooler.

This provides the air coolers housed in the thick cast. Especially, theaftercooler of the three-stage turbocompressor can be incorporated inthe cast which is also provided with the power transmission mechanism,so that sound of the compressed air passed through the passages andsound of toothed gears meshing with each other can be reduced. Thecompressed air passages connecting the respective coolers with thecorresponding compressors can be short in length, which leads toreduction in pressure loss of the compressed air and enhancement of theperformance. Moreover, number of parts can be reduced and space savingcan be attained.

The compressed air passages for communication of the outlets of thefirst and second intercoolers with the inlets of the second- andthird-stage compressors, respectively, are in the form of pipesdetachably attached to the corresponding cooler outlets and to thecorresponding compressor inlets, respectively. This makes it possiblethat a single compressor is applicable for any of three-, two- andone-stage compressions so that the compressor can readily cope withinany pressure range requirement at the demand.

In the three-stage compressor, first and second intercooler and anaftercooler may be arranged and incorporated in an integral cast casingin the order named and partitioned by partitions, an outside of theaftercooler being in the form of arc. This will decrease pressuredifferences between the respective coolers so that stresses on thepartitions can be reduced and stress on the aftercooler can be relieved.

Moreover, an oil tank may be arranged on a side of the integral castcasing, a blowoff silencer being placed between the oil tank and theintegral cast casing so as to be pinched therebetween, the blowoffsilencer being connected to the aftercooler through a blowoff pipe.Because of the blowoff silencer being arranged between the cast and theoil tank charged with lubricant, noise transmitted through a surface ofa housing of the silencer can be reduced and effective space utilizationcan be attained, leading to space saving.

The method for compact assembling of the turbocompressor comprisesintegrally fabricating compressing sections of a three-stage compressorand compressed air passages by casting, and then housing intercoolersand an aftercooler in air-cooler receptacles in the integral cast casingfor incorporation thereof in the integral cast casing, and thenconnecting the intercoolers and the aftercooler with the respectivestage compressors via compressed air passages. The method for compactassembling of the turbocompressor comprises fabricating the integralcast casing with the three air-cooler receptacles partitioned therein,and then housing the first and second intercoolers and the aftercoolerin the three receptacles formed in said integral cast casing forincorporation thereof, the respective coolers being connected to therespective stage compressors thorough the compressed air passages. As aresult, a turbocompressor with three incorporated coolers can be readilyassembled by fabricating the integral cast casing and housing twointercoolers and an aftercooler in cooler receptacles formed in saidintegral cast casing.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view showing a conventional turbocompressor;

FIG. 2 is a sectional view schematically showing a conventional suctionfilter;

FIG. 3 is a schematic view showing a conventional three-stagecompressor;

FIG. 4 is a perspective view partly in section showing an embodiment ofa suction filter according to the invention;

FIG. 5 is a plan view in section looking in the direction of the arrow Vin FIG. 4;

FIG. 6 is a plan view showing an embodiment of a turbocompressoraccording to the invention;

FIG. 7 is a side view of FIG. 6;

FIG. 8 is a side view looking in the direction of arrow VIII in FIG. 7;

FIG. 9 is a side view looking in the direction of arrow IX in FIG. 8;

FIG. 10 is a perspective view showing an integral cast casing in aturbocompressor according to the invention;

FIG. 11 is a plan view in section showing receptacles for air coolersformed in the integral cast casting;

FIG. 12 is a schematic view showing a fundamental structure of theturbocompressor according to the invention;

FIG. 13 is a schematic view showing an application of theturbocompressor according to the invention to two-stage compression;

FIG. 14 is a schematic view showing a further application of theturbocompressor according to the invention to two-stage compression;

FIG. 15 is a schematic view showing a still further application of theturbocompressor according to the invention; and

FIG. 16 is a schematic view showing an application of theturbocompressor according to the invention to one-stage compression.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a suction filter according to the invention will bedescribed with reference to the drawings.

FIGS. 4 and 5 show an embodiment of a suction filter according to theinvention. A casing 19 with suction and discharge sections 20 and 21 isinteriorly provided with a central chamber 23 which is a sealedstructure with required thickness and height. A front or back side ofthe chamber 23 is formed with an opening 24 for communication with thedischarge section 21 and each lateral side surface or each side surfacein the direction of thickness of the chamber 23 is formed with fouropenings 25. A small-diameter cylindrical mount 26 for a filter elementand with peripheral openings is mounted on the surface external of thecorresponding opening 25 and is laterally and horizontally protruded.Detachably fitted over an outer periphery of each of the filter-elementmounts 26 is a small-diameter cylindrical filter element 27. The inflowair via the suction section 20 is laterally separated outside of thechamber 23 to be sucked via each of the filter elements 27, each of thefilter-element mounts 26 and each of the openings 25 into the chamber 23and is discharged from the chamber 23 via the opening 24 into thedischarge section 21 where it is delivered to a suction line 4 (see FIG.1).

The casing 19 has opposite lateral side walls each formed with a window28 larger than an installation region of the four filter elements 27. Asealable lid 29 is attached to the window 28 for free opening andclosing.

Reference numeral 30 denotes a hanging piece for hooking of the suctionfilter according to the invention.

During an operation of the compressor as shown in FIG. 1, the inflow airfrom the suction section 20 of the suction filter 5 according to theinvention is introduced into the chamber 23 after the foreign mattersuch as dust is removed by passing the air through each of the totallyeight filter elements 27, and then the cleaned air is caused to flowfrom the opening 24 via the discharge section 21 to the compressor.Accordingly, the air free from the foreign matter is introduced into thefirst-stage compressor 1. Since the eight filter elements 27 arearranged as two sets of four filter elements on opposite lateral sidesand the inflow air from the suction section 20 is sucked all at once bythe four filter elements 27 on each lateral side, suction resistance ofthe air can be reduced in comparison with a case where all of the eightfilter elements 27 are arranged at a position in a concentrated manner.

When filter elements 27 are to be replaced during operation of thecompressor, all of such filter elements 27 are not required to bereplaced at once by new filter elements 27 but any of the filterelements 27 required to be replaced is singly detached one by one to bereplaced with new one. In this case, the filter element 27 required tobe replaced is detached from the filter-element mount 26; thisdetachment is easily conducted such that the lid 29 on the side wherethe filter element 27 required to be replaced exists is opened to takeout the target filter element 27 from the filter-element mount 26 viathe corresponding window 28. Next, a new filter element 27 or therepaired filter element 27 is attached to the filter-element mount 26from which the filter element 27 has been detached; thus, the one filterelement 27 can be replaced.

In the above, a cover may be attached to the filter-element mount 26 soas to cover the opening on the filter-element mount 26 from which thefilter element 27 has been detached; alternatively, the filter-elementmount 26 may be left as it is without attaching the cover to the mount.

In the case where the cover is not attached to the filter-element mount26 from which the filter element 27 has been detached, the window 28 isclosed by the lid 29 after the filter element 27 required to be replacedis detached and taken out through the window 28 of the casing 19 anduntil the attachment work for the new filter element 27 to the mount 26is started. This causes a part of the sucked air to be sucked throughthe filter-element mount 26 having no filter element 27; however, sincean area of the opening on each of the filter-element mounts 26 is setsmall, an amount of air flowing therethrough is a little, lowering theprobability of the foreign matter being sucked therethrough. A dustremover may be attached to each of the openings 25 as needs demand.

On the other hand, in the case where the opening of the filter-elementmount 26 is covered with the cover to prevent the air from being suckedthrough the opening of the filter-element mount 26 from which the filterelement 27 has been detached, no air is sucked through said mount 26.Accordingly, it is possible to preliminarily prevent the foreign matterfrom being sucked through said filter-element mount 26. Since the inflowair in the casing 19 is sucked through the remaining seven filterelements 27, no trouble occurs on suction of the air.

In the suction filter 5 according to the invention, the filter element27 is divided into eight small-diameter filter elements so as to bearranged in plural positions, which allows each of the individual filterelements to have reduced weight and thus makes the filter elements 27compact in size so as to be easily handled; thus, the replacing work canbe readily conducted manually without using any large-sized machine suchas a crane.

It is to be understood that a suction filter according to the inventionis not limited to the above-mentioned embodiment and that variouschanges and modifications may be effected without leaving the gist ofthe invention. For example, shown in the above are the two sets of fourfilter elements 27 on opposite lateral sides or totally eight filterelements 27; however, the number of the filter elements may be any, notlimited to eight. The respective filter elements 27 shown have equaldiameters; however, the filter elements may have different diameters.

As is clear from the above, a suction filter according to the inventioncan have the following excellent effects and advantages.

(1) Filter elements are separate ones arranged in an air flow path froma suction section to a discharge section, air sucked through each of thefilter elements being introduced into the discharge section; the filterelements may be laterally separately arranged in a casing with suctionand discharge sections, air sucked through the laterally separatedfilter elements being introduced into the discharge section. As aresult, when a filter-element replacement work is to be conductedwithout stopping the air suction, one or some of the filter elements maybe replaced while the suction of the air is continued by the remainingfilter elements. Thus, an amount of air sucked through thefilter-element mount or mounts from which the filter element or elementshave been detached for replacement may be a little, so that aprobability of the foreign matter being sucked can be reduced.

(2) With respect to item (1) above, when the opening on the mount fromwhich the filter element has been detached is closed by a cover, thenthe foreign matter can be prevented from being sucked through theopening on the mount.

(3) The separate filter elements may be arranged on opposite sides of achamber with a sealed structure and provided interiorly and centrally ofa casing, the interior of the chamber being communicated with theexterior of the chamber through each of the filter elements and with thedischarge section. This makes it easy to arrange a lot of filterelements in the opposite sides of the chamber. As a result, each of thefilter elements may be made compact in size, which facilitates handlingof the same upon replacement and makes it possible to make smaller thearea of the opening of the corresponding mount, leading to furtherlowering the probability of the foreign matter being sucked through themount during replacement work of the filter element.

(4) The sides of the casing outwardly of the filter elements may havewindows each having the size corresponding to the grouped filterelements, each of said windows being sealable by a lid which may befreely opened and closed; this makes it possible to easily replace thefilter elements one by one through the window.

An embodiment of a turbocompressor and a method for compact assemblingof the same according to the invention will be described with referenceto the drawings.

FIGS. 6 to 12 show an embodiment of the turbocompressor and the methodfor compact assembling of the same according to the invention. Anintegral cast casing I is provided by integrally casting scrolls 31 a,32 a and 33 a serving as compressing sections of first-, second- andthird-stage compressors 31, 32 and 33, respectively, which constitutetogether a three-stage compressor, receptacles 34 a and 35 a for firstand second intercoolers 34 and 35, respectively, a receptacle 36 a foran aftercooler 36, compressed air passages 37 and 39 introducing thecompressed air from the scrolls 31 a and 32 a to the receptacles 34 aand 35 a, respectively, a receptacle 42 for a power transmittingmechanism, an aftercooler outlet 43 and a blowoff outlet 44. The threeair coolers 34, 35 and 36 are incorporated in the single casting; thatis, the first and second intercoolers 34 and 35 and the aftercooler 36are housed in the receptacles 34 a, 35 a and 36 a of the integral castcasing I. The integral cast casing I has on its one side an oil tank 45.A blowoff silencer 46 is arranged to be pinched between the oil tank 45and the cast casing I. Outlets of the first and second intercoolers 34and 35 are connected to suction ports of the second- and third-stagecompressors 32 and 33 by detachable second- and third-stage suctionpipes 47 and 48, respectively.

More specifically, the three receptacles 34 a, 35 a and 36 a for the aircoolers formed side by side within the cast casing are in parallel witheach other, as is clear from the sectional view of FIG. 11; the firstand second intercoolers 34 and 35 and the aftercooler 36 are housed inthe respective receptacles 34 a, 35 a and 36 a so as to be arrangedlaterally from one end side of the casing in the order named, i.e., inthe order of their lowness in pressure, whereby they are incorporatedside by side in the integral cast casing I. The first and secondintercoolers 34 and 35 and the aftercooler 36 are partitionedrespectively by partitions 49 and 50 having required thickness, thereceptacle 36 a for the aftercooler having an outer side wall 51 in theshape of arc to relieve any stress.

The receptacle 42 for the power transmission mechanism is centrallyformed in the integral cast casing I. Arranged in the receptacle 42 area larger-diameter gear 53 rotated by a drive shaft 52 coupled to a drive(not shown), smaller-diameter speed-up gears 54 and 55 in mesh with thegear 53, a rotary shaft 56 integral with the gear 54, a rotary shaft 57integral with the gear 55 and bearings for rotatably supporting therotary shafts 56 and 57 so as to transmit drive force in enhanced mannerwith increase in speed. Moreover, mounted on one and the other ends ofthe rotary shaft 56 are impellers 58 and 59 which are arranged in thescrolls 31 a and 32 a of the first- and second-stage compressors,respectively. The impellers 58 and 59 are rotated at higher speed by therotary shaft 56 so that compression is conducted in the first- andsecond-stage compressors 31 and 32. Mounted on one end of the rotaryshaft 57 is an impeller 60 which is arranged in the scroll 33 a of thethird-stage compressor. The impeller 60 is rotated at higher speed bythe rotary shaft 57 so that compression is conducted by the third-stagecompressor 33. Further, an upper half cover 61 covering the gears 53, 54and 55 and the rotary shafts 56 and 57 is detachably fitted to an upperopening of the receptacle 42 of the power transmitting mechanism;detachment of the cover 61 makes it easy to access to and conductmaintenance for each part of the power transmitting mechanism.

In the three-stage compressor constituted by the first-, second- andthird-stage compressors 31, 32 and 33 with incorporation of theabove-mentioned power transmitting mechanism and with the rotation ofthe impellers 58, 59 and 60, the compressed air passages 37, 39 and 41integrally fabricated in the integral cast casing I intercommunicate theoutlet of the first-stage compressor 31 and the inlet of the firstintercooler 34, the outlet of the second stage compressor 32 and theinlet of the second intercooler 35, and the outlet of the third stagecompressor 33 and the inlet of the aftercooler 36, respectively. Inplace of the compressed air passages 38 and 40 fixed to the conventionalintegral cast casing shown in FIG. 3, the present invention employssecond- and third-stage suction pipes 47 and 48 which are constructedseparately of the integral cast casing I and which are detachablymounted to the outlet of the first intercooler 34 and the inlet of thesecond stage compressor 32 for intercommunication between them and tothe outlet of the second intercooler 35 and the inlet of the third-stagecompressor 33 for intercommunication between them, respectively. Thus,by the detachable attachment of the second- and third-stage suctionpipes 47 and 48, the three-stage compressor can appropriately cope withtwo- or one-stage compression.

The integral cast casing I is provided, on its one side or its sideadjacent to the drive shaft 52, with an oil tank 45 on which the drive(not shown) is mounted to drive the respective stage compressors 31, 32and 33 through the drive shaft 52; and the blowoff silencer 46 is placedbetween the oil tank 45 and the integral cast casing I so as to bepinched therebetween and located adjacent to the aftercooler 36, thesilencer 46 being connected to the blowoff outlet 44 by a blowoff pipe62.

The blowoff silencer 46 is constructed such that a plurality ofdiffusers 65 a and 65 b are attached to a housing 63 which forms a noisedeadening space 64, a compressed air distribution section 66 beingprovided on an inlet side of the respective diffusers 65 b. Thus, thecompressed air from the blowoff pipe 62 is passed through the diffusers65 a so as to be once reduced in speed and in noise, is passed throughthe distribution section 66, is passed through the diffusers 65 b so asto be reduced in speed and in noise and is allowed to expand in thenoise deadening space 64. Due to bypass through the noise deadeningspace 64, the compressed air is noise-deadened and is discharged througha discharge port 67.

When the three-stage compressor as mentioned above is operated to supplythe compressed air to the demand, the drive force from the drive istransmitted via the drive shaft 52, the gears 53, 54 and 55 and therotary shafts 56 and 57 in the order named to rotate the impellers 58,59 and 60. Thus, the first-, second- and third-stage compressors 31, 32and 33 start to be operated and the air free from the foreign mattersuch as dust is sucked through the suction filter (not shown) into thefirst-stage compressor 31 at its inlet so as to be compressed. Thecompressed air discharged from the first-stage compressor 31 is passedthrough the compressed air passage 37 integrally fabricated in theintegral cast casing I and is introduced into the first intercooler 34so as to be cooled. Then, the compressed air is passed through thesecond-stage pipe 47 and is introduced into the second-stage compressor32 at its suction port so as to be compressed. The compressed airdischarged via the discharge port of the second-stage compressor 32 ispassed through the compressed air passage 39 integrally fabricated inthe integral cast casing I and is introduced into the second intercooler35.

The compressed air from the second intercooler 35 is passed through thethird-stage suction pipe 48 and is introduced into the third-stagecompressor 33 via its suction port so as to be further compressed. Thefurther compressed air discharged via the discharge port of thethird-stage compressor 33 is passed through the compressed air passage41 integrally fabricated in the integral cast casing I, is introducedinto the aftercooler 36, and is then taken out via the outlet 43 of theaftercooler 36 so as to be supplied to the demand.

In the above, the turbocompressor according to the invention, which hasthe two intercoolers 34 and 35 and the single aftercooler 36 or thetotally three air coolers incorporated in the integral cast casing I, isrequired to have no increased installation area in comparison with aconventional three-stage compressor in which an aftercooler is arrangedseparately. Accordingly, space saving can be attained and the number ofthe parts can be reduced; the whole structure can be made compact insize in cooperation with the compressor main parts structured on theintegral cast casing I. Since the first and second intercoolers 34 and35 and the aftercooler 36 are arranged in the order named, it ispossible to shorten the compressed air passages 37, 39 and 41 and thesuction pipes 47 and 48 between the respective stage compressors 31, 32and 33, so that the pressure loss of the compressed air can be minimizedto achieve high performance and low noise. Since the first and secondintercoolers 34 and 35 and the aftercooler 36 are arranged side by sideand are incorporated in the integral cast casing I, the partitions 49and 50 between the intercoolers 34 and 35 and between the intercooler 35and the aftercooler 36, respectively, can be made to have smallerthickness due to the small pressure difference between the coolers; thestress can be relieved outside of the aftercooler 36 since the outerside wall 51 is in the form of arc.

When blowoff is to be conducted during the supply of the compressed airto the demand being stopped, the compressed air is introduced via theblowoff pipe 62 into the blowoff silencer 46 so as to be blown off.During this time, the compressed air from the pipe 62 to the silencer 46is reduced in speed and in noise in the diffusers 65 a and 65 b and isdischarged to the noise deadening space 64 where it is allowed toexpand, and by bypass through the space 64 the compressed air isnoise-deadened, and is discharged. According to the invention, theblowoff silencer 46 is placed to be pinched between the integral castcasing I and the oil tank 45, so that noise transmitted through thesurface of the housing 63 of the silencer 46 can be reduced to furtherimprove the noise deadening effect. Because of its incorporation on theside of the integral cast casing I, the installation space can beeffectively utilized and space saving can be attained in comparison witha case where it is placed separately, thereby contributing tocompactness in size of the whole structure.

When the demand has different compressed-air pressure requirement, it isrequired to cope within the pressure range.

In the turbocompressor according to the invention, the compressed airpassages for intercommunicating the outlet of the first intercooler 34and the suction port of the second stage compressor 32, and the outletof the second intercooler 35 and the suction port of the third stagecompressor 33, respectively, are not integrally fabricated in theintegral cast casing I but are formed as the second- and third-stagesuction pipes 47 and 48 which are detachable. Accordingly, thethree-stage compression mentioned in the above can be readily changedinto two- or single-stage compression.

For example, when the required pressure range is two-stage compression,generally the third-stage suction pipe 48 shown in FIGS. 6-8 is detachedto provide the two-stage compression by means of the first- andsecond-stage compressors 31 and 32. As outlined in FIG. 13, the secondintercooler 35 is used as the aftercooler and the outlet of the secondintercooler 35, as the aftercooler outlet 43. The outlet 43 of theaftercooler 36 shown in FIGS. 6-9 is closed.

This makes it possible to use the compressed air passages 37 and 39integrally fabricated in the integral cast casing I as well as thesecond-stage suction pipe 47 as they are so as to provide the shortestair flow path for the compressed air, advantageously resulting inextremely small pressure loss. The blowoff is conducted by branching thepipe from the outlet of the second intercooler 35, closing the blowoffoutlet 44 of the casing I and using the blowoff pipe 62.

Alternatively, the two-stage compression may be provided by acombination of the first- and third-stage compressors 31 and 33 with nouse of the second-stage compressor 32. In this case, in place of thesecond- and third-stage suction pipes 47 and 48 in FIG. 6, a new suctionpipe 68 (see FIG. 14) is prepared as a pipe longer than the pipes 47 and48 through which the outlet of the first intercooler 34 is directlycommunicated with the suction port of the third-stage compressor 33.FIG. 14 shows Moreover, a combination of two systems may be applied;that is, for example, the two-stage compression using the first- andsecond-stage compressors 31 and 32 may be combined with a boosterconstituted only by the third-stage compressor 33 as shown in FIG. 15.Furthermore, the one- or single-stage compression may be attained bydetaching the second-stage suction pipe 47 shown in FIG. 6 from theoutlet of the first intercooler 34; a compressed air pipe to the demandis connected to the outlet of the intercooler 34. FIG. 16 shows anoutline thereof.

Thus, the respective stage compressors may be freely modified.

It is to be understood that the turbocompressor and the method forcompact assembling of the same according to the invention are notlimited to the embodiments mentioned above and that various changes andmodifications may be made without leaving the gist of the invention. Forexample, the blowoff silencer 46 may be of a structure other thanillustrated. A blowoff valve is, of course, provided in the blowoff pipe62 and is closed during the supply of the compressed air from the outletof the aftercooler 36 to the demand. The suction filter may be installedon the integral cast casing I so as to the structure compact in size.

As mentioned above, the turbocompressor and the method for compactassembling of the same according to the invention can have the followingexcellent effects and advantages.

(1) The integral cast casing with the first-, second- and third-stagecompressors has all the air coolers incorporated which correspond to therespective stage compressors, said respective stage compressors beingconnected to the air coolers through compressed air passages, the aircoolers being incorporated as first and second intercoolers and anaftercooler. As a result, due to the thick cast, sound of the compressedair passed through the passages and sound of toothed gears meshing witheach other can be substantially reduced to minimize undesired noise andto make the structure compact in size. Such compactness in size bringsabout shortness in length of the compressed air passages connecting therespective coolers to the respective stage compressors; as a result, thepressure loss of the compressed air can be minimized to attain highperformance, reduction in number of the parts and space saving.

(2) The compressed air passages for communication of the outlets of thefirst and second intercoolers with the inlets of the second- andthird-stage compressors, respectively, are in the form of pipesdetachably attached to the respective cooler outlets and to therespective compressor inlets, respectively. This makes it possible thata single compressor is applicable for any of three-, two- and one-stagecompression so that the compressor can readily cope within any pressurerange requirement at the demand.

(3) The three air coolers arranged and incorporated in the integral castcasing are first and second intercoolers and an aftercooler in the ordernamed. As a result, the pressure difference between the respective aircoolers becomes small, leading to lower the stress in partitions betweenthe coolers. Since the aftercooler is arranged outermost, arrangementsusing pipes may be readily conducted to apply to various arrangementrequirements. Since the outer side wall of the aftercooler is in theform of arc, the stress relief can be obtained.

(4) The integral cast casing has an oil tank on its side, a blowoffsilencer being pinched between the oil tank and the integral cast casingand being connected to the aftercooler through the blowoff pipe. As aresult, noise transmitted through a surface of a housing of the silencerpositioned between the oil tank and the casting can be substantiallyreduced; it is possible to enlarge the sound reducing effect incomparison with the space; it is possible to shorten the distancebetween the aftercooler and the blowoff silencer, and it is possible toreduce man-hour for the piping work.

(5) In the method for compact assembling of the turbocompressor,integrally fabricated by casting is an integral cast casing withcompressing sections of the three-stage compressor and compressed airpassages, receptacles for the air coolers corresponding to therespective stage compressors being formed in the casing in a partitionedmanner. Then, intercoolers and an aftercooler are housed side by side inthe respective receptacles of the integral cast casing for incorporationthereof, the air coolers being connected to the respective stagecompressors through the compressed air passages. The integral castcasing may be fabricated with three cooler receptacles in a partitionedmanner; then, the first and second intercoolers and the aftercooler arehoused in the receptacles in the order named, the respective coolersbeing connected to the respective stage compressors through thecompressed air passages. As a result, mere fabrication of an integralcast casing makes it possible to obtain the assembly only by assemblingthe power mechanism transmitting the rotating power to the air coolerand to the compressing section, and it is possible to easily assemble.

INDUSTRIAL APPLICABILITY

As mentioned above, the suction filter according to the invention canreduce or prevent suction of the foreign matter upon replacement of thefilter element during the air suction, and makes the replacing workeasy. Further, the turbocompressor and the method for compact assemblingof the same according to the invention can make the three-stagecompressor compact, and make it possible to properly use the three-stagecompressor within a pressure range requirement.

1. A suction filter comprising: separate filter elements arranged in anair flow path from a suction section to a discharge section, air suckedthrough each of said filter elements being introduced into saiddischarge section.
 2. The suction filter as claimed in claim 1, whereinthe filter elements are laterally separately arranged in a casing withsuction and discharge sections, air sucked through said laterallyseparated filter elements being introduced into said discharge section.3. The suction filter as claimed in claim 2, wherein the casing isprovided centrally therein with a chamber which is a sealed structure,the separate filter elements being arranged on opposite sides of thechamber, an interior of the sealed structured chamber being communicatedwith an exterior of the chamber through the respective filter elementsand communicated with the discharge section.
 4. The suction filter asclaimed in claim 2, wherein the casing outside of the filter elementshas sides each formed with a window corresponding to a whole size of thefilter elements arranged on the side, said window being configured to besealed by a lid that can be opened and closed.